Lipids or fatty substances
Lipids or fatty substances are important biochemical substances in plants and animals. Like carbohydrates, lipids comprise carbon, hydrogen, and oxygen. Plant bodies, especially fruits and seeds, store large amounts of lipids. Fatty substances composed of carbon, hydrogen, and oxygen are known as lipids. Chemically, esters of alcohols and fatty acids are called lipids.
Lipids exist mainly in the form of fats and oils. Some lipids are solid at room temperature, and some are liquid at 20°C. Solid and solid lipids are called fats, and liquid lipids are called oils. Lipids have no specific melting point; different fatty substances can be melted at different temperatures. Animal fats, ghee, butter, and milk are the primary sources of lipids that contain a huge amount of fat inside them. On the other hand, in the plant kingdom, lipids are stored in the seeds of mustard, sesame, soybean, coconut, sunflower, almond, olive, palm oil, and many other seeds. Acorns, sheep's wool, sharks, beehives, and whales have a lot of lipids inside their bodies.
The properties of lipids:
1. Lipids are generally colorless, odorless, and tasteless, meaning they don't have a bright color, sharp odor, or taste.
2. They are soluble in ether, alcohol, benzene, chloroform, acetone, petroleum, etc.
3. Lipids are almost insoluble when used in water.
4. They exist as esters of fatty acids.
5. Lipids are lighter than water, so it floats in water and stays on the surface of the water.
6. After hydrolysis, they turn into fatty acids and glycerol.
7. As the molecular weight of lipids increases, lipids' melting point also increases.
8. Lipids have no specific melting point; different type of lipids melts at different temperatures.
9. If the substance Sudan III solution is added to lipids, it gives a red color.
10. At normal temperatures, like in 20°C t 30°C, some lipids such as oils are liquids, and some lipids fat substances are solids.
The structure of lipids
As we all know, lipids generally comprise glycerol and fatty acids. Phospholipids contain phosphorus and nitrogen bases without glycerol and fatty acids. Glycolipids contain fatty acids, sugars such as hexoses, and nitrogenous compounds. Waxy lipids contain alcohol or cholesterol in them instead of glycerol molecules.
Functions of lipids
1. Lipids such as fats and oils are stored in plant bodies as stored food which can be used later. Lipids are taken up as food during the germination of various oilseeds like mustard, sesame, soybean, and many more seeds. More energy in the form of ATP is produced during the process of their oxidation.
2. Phospholipids act as components in various structures of the membrane.
3. Waxy lipids form a layer called cuticle on the outer layer or on the leaf's surface to prevent excessive transpiration or present excessive water loss.
4. Phospholipids act as prosthetic groups in some enzymes and as a carrier of phospholipid ions.
5. Glycolipid molecules play an essential role in photosynthesis.
6. They are linked to proteins to form lipoproteins, and lipoproteins are involved in the energy production process.
Role of Lipids in the bodies of living organisms
- Lipids are stored in the body as food that provides energy.
- Seed grains contain lipids and provide the energy needed during germination.
- Most of the cell membranes are composed of phospholipids.
- Glycolipids play a unique role in the process of photosynthesis.
- Phospholipids also act as cell ion carriers inside our bodies.
- Lipid water-soluble vitamins are B and C, and water-insoluble vitamins are A, D, E, and K.
- Phospholipids act as prosthetic groups for some enzymes in the bodies of living organisms.
- The fat stored under the skin of living organisms acts as a thermal insulator to make them feel warm.
- Certain lipids, such as wax, are present in plant stems and cuticles, reducing transpiration.
- Lipids like terpenes cause fragrance in plants.
Small amounts of protein, hormones, and cholesterol are synthesized from lipids.